This invention relates to a method and means of determining and processing into convenient form tablet formation force data from tablet presses. The invention provides methods for using these data, for example, to monitor and control the operation of the tablet presses. The developed data are also useful for determining the tabletting characteristics of pharmaceutical tablet granulations. This invention is capable of monitoring and controlling one or more tablet presses and virtually any combination of different tablet presses including: presses having a single die, single punch set and single tabletting (station) location (also known as single die-station presses); presses having multiple dies, multiple punch sets and a single tabletting station (also known as multidie, single station presses); presses havng multiple dies and punch sets and also multiple tabletting locations (also known as multidie-station presses); rotary presses; non-rotary presses; high-speed and low speed presses.
The technology of tablet press instrumentation as a production control tool has been commercialized primarily for rotary multidie-station tablet presses to adjust table weight (for example, U.S. Pat. No. 3,255,716, "Measurement of Forces Within a Tabletting Machine"; and U.S. Pat. No. 3,734,663, "Arming Control for Servo Adjusted Tablet Compression Machines"). Devices of this type have been used to obtain a running average of the peak compression forces developed during tablet compression and to use this value in for example a servo system to control the average compression force.
While this type of device may be thought of as providing an adequate method for maintaining the correct average tablet weight, it does not provide, for instance, a system for determining whether individual tablets are underweight or overweight. Therefore, while the average weight of a batch of tablets produced on, for example, a high-speed rotary tablet machine controlled by such a device may be correct, the deviation in weight between individual tablets may be too great in relation to pre-established criteria for the batch of tablets to be acceptable. Such large deviations in tablet weight, which in most instances are detected only during subsequent Quality Control evaluation of the lot of tablets, may be caused by a poorly operatng tablet press, by defective tooling, by undesirable characteristics of the granulation, etc.
It is clear that it would be desirable to determine the standard deviation or some other measure(s) of irregularity in e.g. tablet weight particularly during the actual tabletting of the granulation. It would also be desirable to have a method for testing if tablets were capping during formation. In some instances, it would also be desirable to provide a method for ejecting from the production lot individual tablets whose weight or compression force characteristics did not fall within certain predetermined limits.
When tablet compression forces and ejection forces measured in connection with data processing systems are used as a development tool in granulation formation, they provide valuable information regarding the tabletting characteristics of the granulation, such as compressibility, lubrication, tendency to laminate or cap, flowability of the material, and tendency to stick or adhere to the punch surfaces following tablet formation.
The compression force and ejection force measurement and data processing systems which are currently used in the development of tabletting granulations have been primarily limited to application on low-speed single die-station (i.e. single die, single punch set, single tabletting location or station) tablet presses. Since many production tablet presses are multidie and multipunch set rotary type machines (with one or more tabletting locations or stations), it would be desirable to fully extend the usefulness of these measurement and data processing systems to rotary, multidie and multiple punch set tablet presses, and particularly to the high-speed rotary tablet presses. Specifically, a tabletting granulation which performs well on a low-speed, single die-station machine or a relatively low speed rotary multidie machine may not perform well on a high-speed multidie, single or multiple station rotary machine because of the reduced time available for cavity filling, compression, and ejection in the higher-speed tabletting machines.
Also, existing systems for monitoring and processing compression forces and ejection forces primarily utilize data processing techniques which restrict their application to low speed (up to 5 tablets/sec.) presses. It would, therefore, be desireable to have a data processing system in which the processing electronics automatically adjust to the entire range of press speeds that could be encountered (presently presses run up to roughly 200 tablets/sec.).
Generally, present force monitoring and processing systems are constructed so that only the data processing functions that are initially built into the units can be performed. No provision is made for changing the data processing procedures if an improved or more desirable data processing sequence is determined. It would be desirable to have the capability for modifying the data processing procedure(s) by, for example, reprogramming the set of instructions in a programmable read-only memory and/or making minor hardware modifications to the data processing unit.
In application where it is not necessary to continuously monitor a tablet press, a single system could be used to monitor several tablet presses on a time-sharing basis. In this application a suitable switching system would be employed to control and record the flow of transducer signal information from the several presses to the data processing unit.
On rotary, multidie, single or multiple station tablet machines it is sometimes desirable to isolate a specific die-punch set combination to determine its tabletting characteristics. A primary purpose of this would be to identify a faulty die-punch set combination or, when applying the system to granulation evaluation, to eliminate the effect(s) of different die-punch set combinations in the comparison of different granulations. This cannot be done within the present art.